I've read from different sources about the same battles and the dates of some of the battles are not the same. Is this because some sources didn't consider after the battle skirmishing or some considered the day of retreat of the army or something else?

____________________That old man...had my division massacred at Gettysburg!"
- George Pickett said these words to John S. Mosby shortly after paying Lee a visit in Richmond
"Well, it made you famous"
- Mosby's reply to Pickett